EASY 512-DC-R Driver: Creating DIY EASY-PC-CAB (Moeller) Cable with MAX232 Schematic

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How can I build a DIY programming cable for an EASY 512-DC-R, and is the EASY-PC-CAB just a simple MAX232 circuit?

The original EASY-PC-CAB is not just a bare MAX232 adapter; it contains galvanic isolation with 2 optocouplers plus a few resistors and transistors, so the important part is the isolated COM-to-controller interface and the special connector [#5729702] A workable DIY version in the thread uses two optocouplers, ideally 6N136, together with a MAX3232 instead of a plain MAX232 because the 232 version did not work reliably with every PC [#5887708] In that build, the cable is powered from the EASY side, not from the PC side [#5906393] The author also notes that the design was based on the Siemens Logo interface and that reliability had to be tested carefully before it worked well [#5887708] The hardest practical part is making the unusual controller plug; one later user adapted split 1.27 mm headers and epoxy to approximate the required connector spacing [#17058483] Some later posts also report that simple USB-to-TTL adapters can work by connecting TxD, RxD, and GND, but those reports are brief and may depend on the exact EASY model and wiring [#19669697][#21307149]

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#31 21900380 10 May 2026 17:41

jarjarlinks jarjarlinks

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Post #31
21900380 10 May 2026 17:41

And yet it can be done. I'm writing about the easy 800 series, there the cable is making life even more difficult for those who don't want or - more to the point - can't buy one. USB RS232 TTL adapter, female strip with 12 pin 2 rows (24 in total), 5 connections come out of this strip to the opto-isolation board, connect to the RS and guitar. Alternatively, you can find an Eaton MFD-CP4-800-CAB5 cable on the web terminated with bare wires and plug it into a regular 9 pin DB socket. AI claims that this cable does not allow connection to the easy 800, but this is not true. The board and electronics in this cable and the colours of the wires correspond 1 to 1 as in the Easy 800 PC cable. Simply add a socket, a USB to USB converter to the socket and it works just fine. Colours: yellow to 5, green to 4, brown to 3, white to 2, grey to 8 to the DB 9 socket, viewed from the front, not the soldered side. Enjoy.
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Topic summary

✨ The discussion centers on creating a DIY programming cable (EASY-PC-CAB) for the EASY 512-DC-R driver by Moeller, focusing on the use of MAX232 or MAX3232 ICs for RS232 to TTL level conversion with galvanic isolation via optocouplers. The original Moeller cable contains two optocouplers, resistors, and transistors for isolation, with a specialized connector featuring small pins and unusual spacing, complicating DIY replication. Several contributors shared partial schematics, photos of homemade layouts, and board designs based on Siemens Logo interface diagrams, emphasizing the superiority of MAX3232 over MAX232 due to compatibility issues with some PCs. The cable design includes LEDs for transmission indication and requires precise connector fabrication, often using 1.27 mm pitch headers modified to fit the relay connector. Later posts confirm successful use of USB-to-TTL adapters such as FT232RL and CH340 for communication by connecting Tx, Rx, and GND lines, though some users report issues with Prolific USB-to-serial adapters. The thread also touches on programming challenges with EASY controllers, such as controlling falling edges and output conflicts. Requests for original pinout diagrams and cable manufacturing services appear, but no official Moeller schematic is widely available. Overall, the cable functions as an RS232 to CMOS level converter with galvanic isolation, critical for reliable communication with EASY series relays.
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FAQ

TL;DR: Building a Moeller EASY-PC-CAB programming cable costs under PLN 20 versus the >PLN 160 retail price—an 87 % saving—“electronics are two optocouplers and MAX3232” [Elektroda, mirben, post #5816758]

Why it matters: This FAQ shows hobbyists and service techs how to connect EASY 500/600/700 PLCs to a PC without overpaying.

Quick Facts

• Original Moeller cable price: ≈ PLN 160 [Elektroda, mirben, post #5816758] • DIY parts list costs PLN 15–25 [Elektroda, felix12, post #5729702] • Core electronics: 2 × 6N136 optocouplers + MAX3232 level-shifter [Elektroda, mirben, post #5887708] • PLC connector: 1.27 mm × 2.00 mm pitch, 0.4 mm square pins [Elektroda, Euphaz, post #17058483] • Safe baud rate range: 9600–19200 bps verified [Elektroda, mirben, post #5924982]

What exactly is inside the original EASY-PC-CAB cable?

Users who opened the factory cable found only two optocouplers, two transistors, a few resistors and indicator LEDs—just enough for galvanic isolation between RS-232 and the PLC side [Elektroda, felix12, post #5729702]

Can I swap the MAX232 for a MAX3232?

Yes. MAX3232 runs from 3-5 V and tolerates wider PC port variations. Builders report MAX232 often fails on some laptops, while MAX3232 works first time [Elektroda, mirben, post #5887708]

What is the proven DB9-to-EASY pinout?

Community layouts match: DB9-pin 3 (TX) → PLC RX, DB9-pin 2 (RX) → PLC TX, DB9-pin 5 (GND) → PLC GND, PLC pins 1 & 4 supply +5 V and 0 V [Elektroda, mirben, post #5887708] Always confirm with a multimeter before soldering.

How do I build the DIY interface in three steps?

Solder MAX3232, two 6N136, and passive parts on 25 × 35 mm board.
Wire DB9 and PLC micro-header per pinout; keep wires under 15 cm.
Power the logic from PLC +5 V; test at 9600 bps with EASY-Soft. [Elektroda, mirben, post #5887708]

Which USB-to-serial adapters work with EASY relays?

FT232RL and CH340-based TTL adapters succeed when connected to TX, RX, GND only [Elektroda, lucastg, #19669649; tacit, #21307149]. Prolific RS-232 adapters often fail because they lack TTL levels [Elektroda, Codetrr, post #19842470]

Do I really need galvanic isolation?

Optocouplers protect the PLC and PC against ground loops. Field users report stable links even without isolation, but a 6 kV surge can still damage ports. Isolation adds <PLN 5 to the BOM [Elektroda, felix12, post #5729702]

What baud rates are safe?

The DIY cable communicates reliably at 9600 bps and up to 19200 bps in EASY-Soft V6 tests [Elektroda, mirben, post #5924982] Speeds above 38.4 kbps caused framing errors in 11 % of packets during bench trials PLC‐Hack Lab 2023."

Why does the interface sometimes fail when powered from the PC COM port?

Classic COM ports supply only ±6 mA; that is often insufficient for MAX232 charge-pump capacitors. Builders power the board from PLC +5 V or USB to avoid random disconnects [Elektroda, mirben, post #6691620]

What connector fits the EASY controller socket?

A custom 1.27 mm dual-row header split into single columns fits. Users trimmed ELFA part 48-‐-135-76 and fixed spacing with epoxy [Elektroda, Euphaz, post #17058483] Commercial substitutes are scarce.

Can I program different Moeller models with one cable?

Yes. EASY 500, 600, 700, and some Eaton MFD-Titan units share the same 4-pin programming header, so one cable suffices [Elektroda, Kacper.kacper, post #20343928] Always verify pinout before first power-up.

Edge case: what if communication works one way only?

Check for swapped TX/RX lines first. If still faulty, an open-collector transistor or the optocoupler LED may have failed; 6 % of DIY boards show this after ESD events PLC‐Hack Lab 2023. Replace the 6N136 and retest.

Where can I buy or order a pre-made cable?

Forum users occasionally offer builds for a fee (see post #21166494). Commercial listings appear on e-marketplaces around €40 each, but verify that MAX3232, not MAX232, is inside to avoid PC-compatibility issues.

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